Fluid level detection in containers has traditionally been approached by using container weight, mechanical measurement of fluid height, or by resulting capacitance that the container represents when measured. These approaches can be costly, and may result in questionable accuracy and reliability of measurement. Also, the container, if removable, must be placed on the instrument to determine the amount of fluid contained therein, which can add time to time-sensitive procedures.
Capacitance level sense of fluids has a strong technical foundation, since fluids (particularly water) have a much higher dielectric constant as compared to air or vacuum, and yield a strong signal. Capacitance level sense of removable, portable containers has the challenge of maintaining high accuracy and resolution when using external plates or electrodes. These electrodes, when contacting the outer surfaces of containers, cannot securely and consistently contact the outside of the container. Typically, an air gap between the container and the electrode introduces errors.
Therefore, a low cost, high resolution, and reliable fluid level detection system for fixed and/or removable, portable fluid containers is desired.